630. Cytotoxicity by Adenovirus Replications is Associated with DNA Damages and the Activated P53 Pathways and Is Dependent on Reactive Oxygen Species

Abstract

Adenovirus (Ad) replications induce cytotoxicity to the infected targets but a possible mechanism of replication-induced cell death is not well characterized. We examined cytotoxicity of replication-competent Ads which were activated by an exogenous regulatory region to human pancreatic carcinoma cells with defective p53 pathways. The cytotoxicity was not correlated with infectivity of the Ad vectors or a transcriptional activity of the regulatory regions used to activate the E1 region. Cells infected with the Ads showed cytopathic effects and increased sub-G1 fractions. Caspase-9, less significantly caspase-8 and poly (ADP-ribose) polymerase, but not caspase-3 was cleaved, and expression of the molecules involved in autophagy and caspase-independent cell death pathways, Beclin-1, Atg5, LC3A/B I/II, Endo G, Bid and AIF, remained unchanged. H2A histone family member X molecules were however phosphorylated at Ser 139 after the infection with the Ads, and N-acetyl-L-cystein, an inhibitor for reactive oxygen species, suppressed the Ads-mediated cytotoxicity. We also examined the Ads-mediated cytotoxicity to human esophageal carcinoma cells with mutated p53 gene. Infection with the Ads induced cleavage of caspase-8, -9, -3 and poly (ADP-ribose) polymerase, and increased sub-G1 fractions in the target cells, whereas the infection did not activate autophagy pathways. Transduction with Ads expressing the wild-type p53 gene (Ad-p53) in combination with the replication-competent Ads further enhanced the Ads-mediated cytotoxicity in a synergistic manner. Transduction with Ad-p53 was however inhibitory to production of replication-competent Ad progenies, but the combination augmented Ad-p53-induced p53 expression levels and the phosphorylation. These data collectively showed that an involvement of caspase-dependent apoptosis in the Ads-induced cell death were dependent on cells tested, and that the cell death was linked with DNA damages and actions of reactive oxygen species. Moreover, Ad replications augmented cell death through activation of the p53 pathways.